Your switch issue is because I'm guessing you used the FrSky option when downloading OpenTX but that only applies when you have done the FrSky Mod for telemetry, which you haven't done (or your switch would work)

Start there, flash with a non frsky firmware on your TX

After that it looks like you have calibrated all your ESC's with their minimum VERY high. Likely not the case, but that's what it looks like. How exactly did you calibrate the ESC's?

Also, why are you arming and disarming with both sticks? While I can't see anything in MPNG's docs that would indicate that is a problem it certainly would be with MultiWii.

Also, given you don't really have control of this craft at the moment, do yourself a favor and remove the props until your stick inputs are accurately represented by the motors.

The other thing that just occured to me is that your limits will be way higher now (OpenTX does that by default) and some of your channels may be falling into the failsafe areas (throttle specifically). Try cutting your limits down to + and - 80 or 85 and recalibrate with mission planner

The other thing that just occured to me is that your limits will be way higher now (OpenTX does that by default) and some of your channels may be falling into the failsafe areas (throttle specifically). Try cutting your limits down to + and - 80 or 85 and recalibrate with mission planner